Recently, with increasing consciousness of environmental protection, the movement of recycling and reusing petrochemicals, in addition to conventionally recycled metal materials, has become active. Only in Japan territory, “Waste Disposal Law” (Law No. 137, 1970), “Law for Promotion of Sorted Collection and Recycling of Containers and Packaging” (Law No. 112, 1995), and “Law for Recycling of Specific Household Appliances” (Law No. 97, 1998) have been enforced. As these laws and regulations have been enacted, recycling of thermoplastics of some large household appliances and automobiles has been accelerated.
Many of these recycling activities, however, are thermal recycling using thermoplastics as a heat source and recycling for cascade use in which a lowering of the physical properties of recycled thermoplastics is of little problem. Therefore, little care is taken of sorting of thermoplastics contained in electronic apparatuses, such as copying machines, facsimile machines, personal computers and their peripheral devices (printers, keyboards, and displays), and in expendables (e.g., toner cartridges and ink cartridges) of these electronic apparatuses. As a consequence, thermoplastics to be recycled contain various contaminants, so it is impossible to obtain thermoplastics which can be reused as the same products or parts.
Also, even when electronic apparatuses and their components (to be collectively referred to as electronic apparatuses hereinafter) are manufactured using recycled thermoplastics, these thermoplastics are in most cases used as packaging containers and packing materials. That is, recycled plastic materials are not used to manufacture the original electronic apparatuses. In particular, labels, seals, and decals (to be collectively referred to as labels hereinafter) on which explanation of operation of an electronic apparatus is printed are pasted on external parts of electronic apparatuses. The base material or adhesive of such a label pasted on an external part cannot be removed only by cleaning. At present, the adhesive sticking to the part must be cut away using a cutter or the like, and this increases the recycling cost.
Analogously, an electronic apparatus incorporating an ink holding member for holding ink, represented by an ink-jet apparatus for printing desired character information and image information (to be collectively referred to as image information hereinafter) by discharging ink droplets from discharge orifices onto an arbitrary printing medium, such as paper, cloth, plastic, or metal, or a cartridge containing ink, has a part to which ink and its components have stuck. When this part is directly recycled, the residual ink and its components deteriorate the physical properties and change the hue of the part. This makes recycling of such parts very difficult. Furthermore, these ink-jet apparatuses contain not only inks but also pollutants such as a lubricating agent (e.g., grease) for mechanical driving portions. Hence, these inkjet apparatuses require a more complicated process and a higher recycling cost than those of plastic material recycling that can be commonly thought of. For this reason, no recycling using components of ink-jet apparatuses as materials have been performed.
As methods of recycling in this field, some techniques have been disclosed in Japanese Patent Laid-Open Nos. 5-301222 and 7-323560 and U.S. Pat. No. 2,513,106. The technique disclosed in Japanese Patent Laid-Open No. 7-323560 has disclosed only a method of directly reusing parts to be recycled by cleaning.
The technique disclosed in Japanese Patent Laid-Open No. 5-301222 compensates for a lowering of the physical property values of recycled plastic materials by additives. The technique disclosed in U.S. Pat. No. 2,513,106 compensates for a lowering of the physical property values of recycled plastic materials by polymer selection.
On the other hand, a so-called laser engraving technique is known as a method of displaying desired image information by changing the color of the surface of a plastic part. This technique can print operation instructions of an apparatus directly on a part, so the cost and the number of steps necessary to remove a pasted label can be reduced. Details of this laser engraving technique are described in Japanese Patent Publication Nos. 61-11711 and 62-59663. However, these patent publications have disclosed only the basic techniques of laser engraving and do not exhibit any practical method pertaining to recycling of laser-engraved plastics.
When the physical properties of a material are taken into consideration, the range of use of a recycled material greatly widens if physical property values equivalent to those of its original virgin material are guaranteed. To guarantee physical property values, however, if the addition of additives or the selection of polymers is performed in the recycling process as in the aforementioned prior art, the cost of control of input amounts of additives or the cost of selection of polymers increases the total cost of recycling. This can postpone switching from virgin materials to recycled materials.
Also, as one characteristic of thermoplastics, linear patterns such as black streaks or silver streaks sometimes form on the surface of a molded product owing to the influence of heat applied during molding. These patterns are primarily caused by the molding conditions. However, if foreign matter is mixed in a material itself, a black dot often appears on the surface.
When laser engraving which discolors or carbonizes the surface of an object to be processed is performed, the engraved portion itself can become foreign matter if the object is thermoplastic. Not only in laser engraving but also during use, collection, and disassembly of products, rubbish, dust, and foreign matter adhere to the surfaces of parts to be recycled. If these parts are not sufficiently cleaned and foreign matter is not well removed, larger amounts of foreign matter than when virgin materials are used are produced when these parts are used as recycled materials. This can impair the product value of especially external parts of electronic apparatuses.